Elektron Musical Instruments

The OS is upgradable by .mid or .sys file which you can download 
from the Elektron site.
The latest OS Version is 1.12b

Other than asking generally whether there is anything physically 
wrong with it, I'm not really sure if there's any particular well 
known faults you should ask about.

A tip - I bought mine second hand and I asked the seller for the 
serial number.
I then contacted Elektron by e-mail and they were happy to let me 
know who they sold that serial number MD to, and when and where it 
was shipped to.